Overcurrent device for circuit breakers



July 29, 1958 .1. c. BRUMFIELD 2,845,507

ovERcuRRENT DEVICE RoR CIRCUIT BREAKERS Filed May 28, 1953 2 Sheets-Sheet 1 IEE- 5..

ff O o BY @Imm Y 9M July 29, 1958 J. c. BRUMFIELD 2,845,507

ovERCURRENI DEVICE FoR CIRCUIT BREAKERS 2 Sheets-Sheet 2 Filed May 28, 1953 Tl-E. 5.

United States Patent O 2,345,507 VERCURRENT DEVICE FOR CIRCUIT BREAKERS John C. Brumield, Philadelphia, Pa., assigner to I-T-E Circuit Breaker Company, Philadelphia, Pa.

Application May 28, 1953, Serial No. 357,963

3 Claims. (Cl. 20G-88) My invention relates to circuit breakers and is more particularly directed to a novel time delay and instantaneous overcurrent tripping unit.

Molded case circuit breakers are provided with a time delay tripping unit usually in the form of a bimetallic element and an instantaneous trip unit which is usually in the form of' a magnetic yoke-armature combination.

On the occurrence of an overcurrent, deflection of the bimetal will be effective to delatch the cradle mechanism and on the occurrence of a fault current, the magnetic yoke will be sufficiently energized to attract its armature thereby resulting in delatching of the cradle mechanism to effect contact disengagement.

' When this type of instantaneous and time delay overcurrent device is used in a m-olded case circuit breaker, it is essential that it be compact and still have suflicient space in order to impart a hammer blow on the common tripper bar of the protective device.

Many combinations of time delay and instantaneous overcurrent devices have heretofore been proposed. However, these arrangements were constructed so that the magnetic yoke and or the armature were mounted on the bimetallic element. This had the inherent disadvantage of adding mass to both of the trip units thereby substantially reducing the time of operation. Furthermore, in this prior art arrangement when either the magnetic yoke or armature was secured to the already hardened and tempered bimetallic element, the characteristics of same would be changed and thus, c-onsiderable work and effort was involved to obtain proper calibration of the time delay unit. That is, change in characteristics of the time delay bimetallic device results whenever it is necessary to secure or attach a second member thereto.

In still other arrangements heretofore known in the art, the magnetic yoke or armature was attached to or pivoted to the latch or has lost motion with respect to the latch. However, none of these arrangements have proved successful for application with molded case eircuit breakers.

In the novel overcurrent device of my invention, the instantaneous magnetic means is mechanically independent of the time delay bimetallic element and utilizes the bimetal as a single turn for the energization of the magnetic yoke. By this arrangement, it is possible to not only achieve a true hammer blow elfect by the armature on the common tripper bar but also eliminates any variation or change in the characteristic of the bimetallic element since no members are secured thereto. Furthermore, this arrangement has a minimum number of moving parts since magnetic yoke is rigidly secured in an appropriate recess of the housing. That is, the magnetic yoke and bimetal are positioned in a pocket of the molded base and a single screw mounts these two units and electrically connects them to a conductor.

The magnetic pole faces are shaped to produce a maximum pole face relative to the armature and to produce ICC , 2 an air gap relative to the armature which is less than the travel of this unit during the tripping operation.

The armature is mounted upon a shaft which in turn is rotatably mounted on bearings. The bearings rest in aA pocket in the molded base and in turn are retained by an insulating barrier which rests in slots of the housing and may be retained bythe cover thereof. Thus, the assembly of the parts is very simple as they may be merely placed in position in the molded housing and the covering fastened thereto to retain them in position.

Biasing means are provided for the armature to urge it away from the pole face of the magnetic yoke and the tripper bar. On the occurrence of a fault current, the armature will close against the magnet and engage common tripper bar with a hammer blow. On the occurrence of an overcurrent, deflection of the bimetal will cause engagement with the common tripper bar thereby rotating this unit. A standard type of calibration or adjusting screw may be placed on the bimetallic element.

Accordingly, a primary object of my invention is to provide a novel overcurrent device in which the instantaneous and time delay portions thereof are mechanically independent.

Another object of my invention is to provide a magnetic instantaneous trip device which is mechanically independent of the thermal time delay trip unit so that a hammer blow on a common tripper bar from the armature of' the magnetic means will not be decreased or affected by the time delay element.

Afurther object of my invention is to provide an overcurrent device which is relatively simple in construction, compact and relatively inexpensive.

A still further object of my invention is to provide time delay and instantaneous current responsive means which are independent of each other.

Another object of my invention is to provide a combined time delay and instantaneous overcurrent device in which the magnetic yoke is permanently mounted in an appropriate recess of the molded housing and secured in position by means of a screw which both secures the bimetal and provides for terminal connections thereto.

Another object of my invention is to provide an overcurrent device having botn instantaneous and time delay characteristics in which the mounting of the instantaneous portion is completely independent from the time delay portion.

These and other objects of my invention will be apparent from the following description when taken in connection with the drawings in which:

Figure 1 is a top View of a circuit breaker in which my overcurrent device may be utilized. This figure illustrates a three pole circuit breaker with the cover removed and incorporates my present invention.

Figure 2 is a side sectional View taken along the lines 2-2 of Figure l and illustrates the position of my overcurrent device and the operating mechanism of the circuit breaker when the circuit has been tripped due to an overcurrent.

Figure 3 is a perspective view of my novel overcurrent device illustrating the mechanical independent mounting of the instantaneous armature and time delay bimetal.

Figure 4 is an end view of my overcurrent device.

Figure 5 is a side View of my novel overcurrent device illustrating the relationship of the instantaneous armature and bimetallic time delay means with respect to the common tripper bar.

Figure 6 is a View taken in the direction of the arrows 6--6 of Figure 5 and illustrates the position of the armature bearing and barrier with the bimetallic element and magnetic yoke removed.

Figure 7 is a View taken in the direction of the arrows 3 7-7 of Figure 4 and illustrates the position of the latch with respect to the tripper bar when normal load current is flowing through the circuit to be protected.

Referring first to Figures l and 2 showing a three pole embodiment of a circuit breaker in which my invention can be adapted, the housing of the circuit breaker 10 is preferably made of a plastic substance and is provided with appropriate openings 21 and 22 through which the circuit breaker terminals 25-26, respectively, are substantially brought out of housing 20 to be engaged by the line terminals of the line to be protected. This circuit breaker may be of the type shown in U. S. Patent 2,673,908 to John C. Brumeld entitled Instantaneous Trip Circuit Breaker and assigned to the assignee of the instant application.

The housing 20 consists of two sections, a base 20a which is a section of the housing 20 on which the various components of the circuit breaker 10 are mounted as Ihereinafter described and a cover 20b which completely closes the circuit breaker 10 by tightly engaging the base 28.

In the three pole circuit breaker 10 which is being considered for this example, there will be three sets of circuit breaker terminals 25 and 26. However, for the sake of clarity, only the center phase B of the three pole circuit breaker 10 having phases A, B and C will be described.

Considering then this center phase B of the three-pole circuit breaker 10, the circuit breaker terminal 25B rests against an extending shoulder 28B of molding 20a. Shoulder 28B is centrally perforated at 29B to house eventually a bolt and a nut (not shown) to secure the line terminal (not shown) to circuit breaker terminal 25B. As previously mentioned, circuit breaker terminal 25B extends through opening 21B into base 20a. Circuit breaker terminal 25B is shaped like an angle, one side 30B of the angle being used to receive a line terminal (not shown), while the other side 31B is soldered or in any other way connected to a pigtail or conductor 35B.

Pigtail 35B is rigidly secured to the free end of the bimetal 38B at the calibration screw 43B. As best seen in Figures 3 `through 7, the L-shaped thermal responsive means 38B has one leg thereof positioned on top of the substantially U-shaped magnetic yoke 200. A screw 201 is passed through the terminal 48B of the pigtail 52B through one leg of the bimetal 38B into the molding 20. Thus, the screw 201 secures both the bimetallic element 38B and the magnetic yoke 200 to the base molding 20 and also serves to electrically connect the terminal 48B to the bimetallic element 38B. Thus, a complete current path is provided from the pigtail 52B to the terminal 48B and out the pigtail 35B to thereby form a single turn for the energization of the magnetic yoke 200.

A pivotally mounted shaft 203 mounted in bearings 204, 205 contains wire spring 206. A barrier plate 209 positioned within appropriate recesses of the groove in base molding 20 for the overcurrent device serves as a stop for one end of the wire spring 206.

The armature 211 is secured to the rotatably mounted shaft 203 at the area which contains the wire spring 206 and serves as a stop for the opposite end of this wire spring. It will be noted that the wire spring 206 may be mounted on either side of the armature 211 rather than being mounted in the center as shown in Figure 3. Thus, with only one end of the spring 206 engaging the armature 211, it will not be necessary to reduce the crosssectional area of the shaft 203 to mount the spring. Thus, as best seen in Figure 5, the armature 211 is biased in a counterclockwise direction around the shaft 203 due to the wire spring 206. The bottom ledge of the barrier 209 serves as a stop to limit the counterclockwise rotation of the armature 211.

The enlarged magnetic section 213 of the armature 211 is positioned above the pole faces 214 and 215 of the magnetic yoke 200. rent, the single turn comprising the current ow through On the occurrence of a fault cur' 4 the bimetal 38B will sufficiently energize the magnetic yoke 200 so that the portion 211 of the armature 213 will be attracted toward the pole faces 214 and 215. That is, the armature 211 will be rotated in a Iclockwise direction against the bias of the wire spring 206. The protruding portion 216 of the armature 211 will then be driven against the protrusion 60B of the common tripper v bar 65.

As will hereinafter be apparent, the counterclockwise rotation of the common tripper bar 65 will effect disengagement of the latch 147B-152B to thereby effect disengagement of the cooperating contacts 77-85.

It will be noted that the movement ofthe armature 211 when attracted by the magnetic pole 200 is completely independent of the movement of the bimetal 38B and hence, clockwise rotation thereof will result in a hammer blow on the protrusion 60B of the common tripper bar 65 to effect contact disengagement.

A portion 66B of the common tripper bar 65 is positioned in alignment with the adjustment screw 43B of the thermal element 38B. Thus, on the occurrence of an overcurrent, the bimetal 38B will deect to the right, as seen in Figure 2, to thereby engage the portion 66B and cause counterclockwise rotation of the common tripper bar 65.

It will be noted that when the circuit breaker is tripped due to the occurrence of an overcurrent condition, the

bimetallic element 38B will deflect to the right and its movement Will be independent and unaffected by the instantaneous magnetic trip means 200-211.

The common tripper bar 65 provided at phase B as above noted has an extending member having portions 60B and 66B which are respectively engaged by the portion 216 and the armature 211 and the adjustment screw 43B and the bimetal 38B.

The pigtail 52B to the fault current responsive means 38B and 211 is electrically connected in any suitable way to the end 71B to the arm 71B. Movable contact arm 71B is pivoted by means of the pivot pin 72B engaging aligned openings 73B of the metallic frame or support 75B. r

Contact arm 71B is provided at its other end with a substantially rectangular shaped contact slab 77B. Contact slab 77B made of good conducting material is rigidly secured to contact arm 71B by means of a rivet 78B or in any other suitable way.

Stationary Contact 80B consists of a rectangular section metallic member 81B having at the end nearer to contact arm 71B a stationary contact slab 85B rigidly secured to member 81B. Member 81B is secured to housing 20 of thte circuit breaker through a screw 86B and la washer 87B.

Stationary contact 80B is also provided with a terminal extension 26, an integral part of metallic member 81B,`

which extends for a portion 90B out of housing 20 to permit by means of screw means (not shown) the conneotion of a line terminal to circuit breaker terminal 26.

Stationary contact 80B is also provided with an arc extinguishing chamber B or arc chute having a number of arc extinguishing plates 96B so that at the opening portion of the circuit breaker the arc existing between contact slab 77B and contact slab 85B is extinguished before producing damage to the contact slabs 77B and 85B.

The operating mechanism of the circuit breaker, which forms no part of my present invention, is described in the aforementioned U. S. Patent 2,673,908.

T-member B is provided at its upper portion 122B with a substantially rectangular extension 131B. Upper portion 122B of T-member 120B is slotted yin its mid portion and provided with raised member 132B cut out from the upper portion 122B of T-member 120B which serves to be engaged by a plastic operating handle 135B for manually opening and closing the circuit breaker, as hereinafter described.

One leg 155B of the V-shaped cradle 145B is shaped as shown in Figure 2 to engage a latch 147B. Latch 147B is provided with a slot 148B engaged by pin 150B around which latch 147B can ro-tate and can also have translational motion. ILatch 147B is provided with a pointed end 151B latched under normal conditions by a latch surface 152B on the tripper bar 65.

Latch surface 125B is composed `of a thin strip of material on tripper bar 65 supporting the latch 147B. The leg 157B of V-shaped member 145B is pro-vided with a cylindrical hole engaged by a pivot pin 106B secured to the raised portion 165B of frame 75B. Leg 175B of V-shaped member 145B is provided at the bottom of the V with a shoulder extension 166B. Raised portion 165B of frame 7 5B is provided with an opening through which passes contact slab 77B of movable contact arm 71 and provides a stop for V-shaped cradle 145B.

Near the end 70B of movable contact arm 71B at which pigtail 52B is connected, an essentially rectangular section bar 180 is rigidly secured to movable contact arm 71B in any suitable way. Shaft or tie bar 180 is common to all three phases A, B and C of the three-pole circuit `breaker, being rigidly secured to the ends 70 ofthe movable contact arm 71 of every phase so that if one movable contact, for example, 71B, is moved whether opened or closed, the other two movable contact arms 71A and 71C will simultaneously perform the same movements.

The circuit breaker 10 is also provided around arc chute 95B with an insulation 185B for completely insulating arc chute 95B.

Thus, it will be seen that when either the time delay or instantaneous overcurrent means rotates the common tripper bar 65, in `a clockwise direction, both the latch 147B and 187B will be released and hence, spring 118 will drive the contacts 77 to disengaged position.

As heretofore noted this trip of the circuit breaker to the position -indicated in Figure 2 by the release of the two latches can be achieved by either an overc-urrent which will cause deliection of the bimetal 38B to the right and result in engagement of the adjustment screw 43B with the protrusion 66B to cause counterclockwise rotation of the tripper bar 65 or due -to a fault current condi-4 tion wherein the single turn of the bimetal 38B will suciently energize the magnetic pole 200 to thereby rotate the armature 211 in a clockwise direction against i-ts bias 206 thereby bringing its extension 216 into engagement with the protruding portion 60B to rotate the tripper bar in a counterclockwise direction.

Thus, it will be seen that with the novel overcurrent device of my invention, the instantaneous trip means comprising the armature 213 and the magnetic yoke 200 are mechanically independent of the time delay thermal means 38B and hence, the occurrence of a fault current or an overcurrent will result -in a blow or force in one direction on the tripper bar 65 to result in the tripping of the circuit breaker.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of thte principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. In a circuit breaker having a base and a pair of cooperable contacts; one of said contacts being biased to open position; a thermally responsive element compris- Iing a bimetal; one portion of said bimetal being rigidly supported on said circuit breaker base and the other portion being free to flex when heated; said thermally responsive element being connectible into an electric circuit to be protected by said circuit breaker; a magnet mounted adjacent to and secured to the rigid portion of said ybimetal and rigidly held in place; a trip latch spaced 6 from said bimetal to maintain said biased contact in its contact engagement with the other of said cooperable contacts; the `flexible portion of said bimetal when operated engaging and operating said trip latch to release said contacts for operation by its bias; an armature being mounted independently of and spaced from both said bimetal and said trip latch; said armature being operated by said magnet when fault current flows through said bimetal and energizes said magnet; said armature being operatively positioned to engage and operate said trip latch; said armature and bimetal bein-g free to operate said trip latch mechanically and electrically unrestrained by the other.

2. IIn a circuit breaker having a base and a pair of cooperable contacts; one of said contacts being biased to open position; a thermally responsive element comprising an L-shaped bimetal; one portion of said bimetal being rigidly supported on said circuit breaker base and the other portion being free .to flex when heated; said thermally responsive element being connectible into an electric circuit to be protected by said circuit breakers; a magnet being mounted adjacent the rigid portion of said bimetal and rigidly held in place; a trip latch spaced from said bimetal to maintain said contact in its contact engagement with the other of said cooperable contacts; the ilexible portion of said bimetal when operated engaging and operating said trip latch to release said contacts for operation by its bias and an armature spaced from said bimetal and operated by said magnet when fault current flows through said bimetal and energizes said magnet; said armature when operated engaging and operating said trip latch; and a commonfastening means for the rigid portion of the bimetal and magnet; said fastening means also providing a terminal connection from the bimetal to the circuit to be protected; said armature and bimetal being free-to operate said trip latch mechanically and electrically unrestrained by the other.

3. lIn a three pole circuit breaker having a base and three pairs of cooperable contacts, one contact from each of said three pairs of contacts being biased to open position; a thermally responsive element for each pole comprising an L-shaped bimetal, one leg of said bimetal being rigidly supported on said circuit breaker base and ythe other leg flexing when heated; said thermally responsive elements being connectible into an electric circuit to be protected by said circuit breaker; an electromagnet rigidly mounted adjacent the rigid portion of each of said bimetals and encompassing each of said bimetals; a trip latch to maintain said biased contacts in engagement with the remaining contact in each pair of said cooperable contacts; va common trip bar for said circuit breaker, said trippcr bar containing a portion of said trip latch; the flexible portion of each of said bimetals when operated directly engaging said tripper bar and thereby operating said trip-latch to release each of said contacts for operation by its bias; armatures individually operated by each `of said electromagnets when fault current ows through said bimetals and energizes said electromagnet; said armatures when individually Ioperated directly engaging said tripper bar and thereby operating said trip latch; said :armatures and said bimetals each being free to operate mechanically and electrically unrestrained by the other.

References Cited in the le of this patent UNITED STATES PATENTS 2,043,306 Sandin June 9, 1936 2,050,285 Dorfman Aug. 11, 1936 2,089,716 Smith Aug. 10, 1937 2,294,838 Dorfman Sept. l, 1942 2,328,458 Jackson et al. Aug. 31, 1943 2,458,151 Dorfman et al. Jan. 4, 1949 2,673,264 Cole Mar. 23, 1954 

